JP2015013724A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a decrease in image quality due to a sliding contact between a resistance portion such as a separation pad and a sheet.
A first conductor 21A is provided in a sheet conveyance path from a separation pad 19C of a second feeder mechanism 19 to a transfer unit 13 so as to come into contact with a portion in contact with the separation pad 19C. Accordingly, even if the separation pad 19C is in sliding contact with the sheet and the sheet is charged, the first conductor 21A can remove the charge. Accordingly, it is possible to suppress a decrease in image quality due to the sliding contact between the separation pad 19C and the sheet.
[Selection] Figure 1

Description

  The present invention relates to an electrophotographic image forming apparatus.

  For example, in the image forming apparatus described in Patent Document 1, a plurality of sheets fed from a multi-purpose sheet feeding tray (also referred to as a multi-purpose tray) are separated and transferred one by one by a separation roller and a separation pad. It is transported to the department side.

  The separation roller rotates while imparting a conveyance force to the sheet to the transfer unit side. The separation pad is disposed at a position facing the separation roller, and is brought into contact with the sheet from the same side as the transfer portion to impart a conveyance resistance due to friction. As a result, the sheet on the separation pad side stops, only the sheet in contact with the separation roller is sent out to the transfer unit side, and a plurality of sheets are separated one by one.

JP 2006-315797 A

  Since the separation pad imparts conveyance resistance to the sheet by friction, at least a portion of the sheet conveyed to the transfer unit that is in sliding contact with the separation pad (hereinafter also referred to as sliding contact) is frictionally charged.

  A charge having a polarity opposite to that of the developer is applied to the transfer portion. Then, the transfer unit transfers the developer image onto the sheet using an electrostatic attraction generated between the developer and the transfer unit. For this reason, when the separation pad is in sliding contact with the sheet from the same side as the transfer portion, the transfer of the developer image may be hindered due to frictional charging caused by the sliding contact, and the quality of the formed image may be lowered. .

  The present invention has been made in view of the above points, and it is an object of the present invention to suppress deterioration in image quality caused by a sliding contact between a resistance portion such as a separation pad and a sheet.

  In order to achieve the above object, the present invention is an electrophotographic image forming apparatus for forming an image on a sheet, and a transfer section (13) for transferring a developer image to the sheet, and a rotation in contact with the sheet And the separation roller (19B) for feeding the sheet to the transfer portion (13) side, and a position facing the separation roller (19B). The sheet contacts the sheet from the same side as the transfer portion (13) and is caused by friction. A resistance part (19C) for imparting conveyance resistance and a sheet conveyance path from the resistance part (19C) to the transfer part (13), and at least a position where the resistance part (19C) is in contact with the conveyed sheet It is the 1st conductor which contacts, Comprising: At least the site | part which contacts a sheet | seat is provided with the 1st conductor (21A) comprised with the electrically-conductive material, It is characterized by the above-mentioned.

  Thereby, in this invention, even if a resistance part (19C) slidably contacts with a sheet | seat and the said sheet | seat is charged, the said sheet | seat can be neutralized by the 1st conductor (21A). Accordingly, it is possible to suppress a decrease in image quality due to the sliding contact between the resistance portion (19C) and the sheet.

  Incidentally, the reference numerals in parentheses for each of the above means are examples showing the correspondence with the specific means described in the embodiments described later, and the present invention is indicated by the reference numerals in the parentheses of the above respective means. It is not limited to specific means.

1 is a central sectional view of an image forming apparatus according to a first embodiment of the present invention. 6 is an enlarged view of a sheet conveyance path from a second feeder mechanism 19 to a transfer unit 13. FIG. It is a figure which shows the width direction dimensional relationship of the separation pad 19C and the 1st conductor 21A. It is a center sectional view of an image forming apparatus concerning a 2nd embodiment of the present invention.

  The “embodiment of the invention” described below shows an example of the embodiment. In other words, the invention specific items described in the claims are not limited to the specific means and structures shown in the following embodiments.

In this embodiment, the present invention is applied to an electrophotographic image forming apparatus. Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In addition, the arrow etc. which show the direction attached | subjected to each figure were described in order to make it easy to understand the relationship between each figure, and this invention is not limited to the direction attached | subjected to each figure. Absent. At least one member or part described with at least a reference numeral is provided, except where “plurality”, “two or more”, and the like are omitted.

(First embodiment)
1. Outline of Image Forming Apparatus As shown in FIG. 1, an image forming unit 5 that forms an image on a sheet is accommodated in a housing 3 of the image forming apparatus 1. The image forming unit 5 is an electrophotographic system having a developing cartridge 7, a photosensitive drum 8, an exposure device 9, a fixing device 11, and the like.

  At the upper part of the housing 3, a discharge port 3A and a discharge tray 3B are provided. The discharge port 3A is a part through which the sheet on which the image is formed is discharged. The discharge tray 3B is a placement unit on which the sheet discharged from the discharge port 3A is placed.

  The developing cartridge 7 includes a developing roller 7A, a storage portion 7B, and the like. The photosensitive drum 8 carries a developer image. The charger 8A charges the photosensitive drum 8. The exposure device 9 exposes the charged photosensitive drum 8. Thereby, an electrostatic latent image is formed on the photosensitive drum 8.

  The developing roller 7A supplies the developer stored in the storage unit 7B to the photosensitive drum 8. As a result, a developer image is formed on the photosensitive drum 8. A transfer unit 13 is disposed at a position facing the photosensitive drum 8.

  The transfer unit 13 transfers the developer image carried on the photosensitive drum 8 to a sheet. A charge having a polarity opposite to that of the developer is applied to the transfer unit 13. The developer image is transferred to the sheet by electrostatic attraction generated between the developer and the transfer unit 13.

  The fixing device 11 directly or indirectly heats the developer transferred to the sheet, and fixes the developer image on the sheet. A first feeder mechanism 15 and a second feeder mechanism 19 are provided upstream of the image forming unit 5 such as the transfer unit 13 in the sheet conveyance direction.

  The first feeder mechanism 15 sends out the sheets placed on the paper feed tray 17 one by one toward the image forming unit 5 side. The first feeder mechanism 15 includes a pickup roller 15A, a separation roller 15B, a separation pad 15C, and the like.

  The pickup roller 15A sends out at least one sheet out of the sheets placed on the paper feed tray 17 to the separation roller 15B side. The separation roller 15B rotates in contact with the sheet sent out by the pickup roller 15A, and sends the sheet to the transfer unit 13 side.

  The separation pad 15C is disposed at a position facing the separation roller 15B. Then, the sheet is brought into contact with the sheet from the same side as the photosensitive drum 8 to impart a conveyance resistance due to friction to the sheet. For this reason, the sheet on the separation pad 15C side stops, and only the sheet in contact with the separation roller 15B is conveyed toward the image forming unit 5.

  The paper feed tray 17 is detachably attached to the apparatus main body below the image forming unit 5 in the apparatus main body. The apparatus main body refers to a portion that is not disassembled by the user when the housing 3 or the frame (not shown) is used.

  The second feeder mechanism 19 sends out the sheets placed on the multipurpose sheet feeding tray (not shown) one by one toward the image forming unit 5 side. The multipurpose paper feed tray is provided in a cover 3 </ b> C provided on the front side of the image forming unit 5 in the housing 3.

  The second feeder mechanism 19 also includes a pickup roller 19A, a separation roller 19B, a separation pad 19C, and the like. The pickup roller 19A sends at least one sheet out of the sheets placed on the multipurpose sheet feeding tray to the separation roller 19B side.

  The separation roller 19B rotates in contact with the sheet sent out by the pickup roller 19A, and sends the sheet to the transfer unit 13 side. The pickup roller 19 </ b> A and the separation roller 19 </ b> B contact the sheet from the same side as the photosensitive drum 8 and apply a conveying force to the sheet.

  The separation pad 19C is disposed at a position facing the separation roller 19B. Then, the sheet is brought into contact with the sheet from the same side as the transfer unit 13 to impart a conveyance resistance due to friction to the sheet. Thereby, also in the 2nd feeder mechanism 19, similarly to the 1st feeder mechanism 15, a some sheet | seat is isolate | separated one by one, and is conveyed to the image formation part 5 side.

  As shown in FIG. 2, a first conductor 21 </ b> A electrically connected to the ground side is provided in the sheet conveyance path from the separation pad 19 </ b> C to the transfer unit 13. In the first conductor 21 </ b> A, at least a part of the sheet conveyed from the second feeder mechanism 19 that comes into contact with the part where the separation pad 19 </ b> C is in contact is made of a conductive material.

  That is, as shown in FIG. 3, the separation pad 19 </ b> C is made of a material having a plate-like portion in contact with the sheet and having a large coefficient of friction such as cork. The width direction dimension W1 of the first conductor 21A is larger than the width direction dimension W2 of the separation pad 19C. Note that the width direction is a direction orthogonal to the sheet conveyance direction and parallel to the sheet surface on which an image is formed.

  As shown in FIG. 2, a second conductor 21B made of a conductive material is provided at a position facing the first conductor 21A. The second conductor 21B contacts the sheet from the sheet surface opposite to the first conductor 21A, that is, the surface on which an image is formed. In the present embodiment, the width direction dimension of the second conductor 21B is the same as the width direction dimension W1 of the first conductor 21A.

  An electric circuit that electrically connects the first conductor 21A and the ground side, and an electric circuit that electrically connects the second conductor 21B and the ground side have an electric resistance having a predetermined electric resistance set in advance. Resistor portions R1 and R2 are provided, respectively. In the present embodiment, the resistance value of the electric resistance portion R1 is larger than the resistance value of the electric resistance portion R2.

  The first conductor 21A and the second conductor 21B according to the present embodiment are rotatable rollers having at least an outer peripheral surface made of metal. The first conductor 21A and the second conductor 21B are pressed against the sheet so as to generate a contact surface pressure of a predetermined level or more, and are driven to rotate as the sheet moves.

  A registration roller 23 </ b> A and a pinch roller 23 </ b> B are provided in the sheet conveyance path from the first conductor 21 </ b> A and the second conductor 21 </ b> B to the transfer unit 13. The pinch roller 23B presses the sheet against the registration roller 23A and sandwiches the sheet in cooperation with the registration roller 23A.

  The registration roller 23A and the pinch roller 23B rotate and stop in conjunction with each other, thereby temporarily stopping the conveyance of the conveyed sheet, and then restarting the conveyance of the sheet at a predetermined timing set in advance.

  Accordingly, the sheet conveyed toward the image forming unit 5 from the first feeder mechanism 15 or the second feeder mechanism 19 enters the image forming unit 5 at a predetermined timing after the posture is corrected.

2. Features of the Image Forming Apparatus According to the Present Embodiment In the present embodiment, the first conductor 21 </ b> A that comes into contact with the location where the separation pad 19 </ b> C contacts is provided in the sheet conveyance path from the separation pad 19 </ b> C to the transfer unit 13. It is characterized by that.

  Thereby, in this embodiment, even if the separation pad 19C is in sliding contact with the sheet and the sheet is charged, the sheet can be neutralized by the first conductor 21A. Accordingly, it is possible to suppress a decrease in image quality due to the sliding contact between the separation pad 19C and the sheet.

  The present embodiment is characterized in that an electrical resistance portion R1 is provided in an electrical circuit that electrically connects the first conductor 21A and the ground side. Thereby, even if a leakage current is generated from the transfer unit 13 to the sheet side, the leakage current can be prevented from flowing out of the first conductor 21A.

The present embodiment is characterized in that a second conductor 21B made of a conductive material is provided at a position facing the first conductor 21A. Thereby, the sheet can be reliably discharged.
(Second Embodiment)
In the present embodiment, a sheet conveyed by any one of the first feeder mechanism 15 and the second feeder mechanism 19 is in contact with the first conductor 21A and the second conductor 21B. Thus, the sheet can be discharged from any feeder mechanism.

  Specifically, the first conductor 21A and the second conductor 21B are, as shown in FIG. 4, a transport path L1 configured by the first guide portion 15D and a transport path L2 configured by the second guide portion 19D. Are provided on the transfer unit 13 side from the portion where the two are joined.

  The first guide unit 15D guides the sheet fed from the paper feed tray 17 by the first feeder mechanism 15 to the transfer unit 13 side, and configures the transport path L1. The second guide portion 19D guides the sheet sent out by the second feeder mechanism 19 to the transfer portion 13 side, and configures the transport path L2.

(Other embodiments)
Although the image forming apparatus according to the above-described embodiment is a direct method in which the developer image carried on the photosensitive drum 8 is directly transferred to a sheet, the present invention is not limited to this.

  That is, the present invention is, for example, an intermediate transfer type color electrophotographic image in which a developer image carried on the photosensitive drum 8 is transferred to a transfer belt and then the developer image transferred to the transfer belt is transferred to a sheet. It can also be applied to a forming apparatus.

  The image forming apparatus according to the above-described embodiment is a monochrome electrophotographic system, but the present invention is not limited to this, and for example, a direct tandem or intermediate transfer type color electrophotographic image forming apparatus is also used. Applicable.

  In the above-described embodiment, the electric resistance portions R1 and R2 are provided in the electric circuit that electrically connects the first conductor 21A and the second conductor 21B and the ground side. However, the present invention is not limited to this. Instead of this, the electric resistance portions R1 and R2 may be abolished, or one of the electric resistance portions may be abolished.

  In the above embodiment, the resistance value of the electric resistance portion R1 is larger than the resistance value of the electric resistance portion R2, but the present invention is not limited to this, and the resistance value of the electric resistance portion R1. And the resistance value of the electrical resistance portion R2 may be the same, or the resistance value of the electrical resistance portion R1 may be equal to or less than the resistance value of the electrical resistance portion R2.

  In the above-described embodiment, the first conductor 21A and the second conductor 21B are electrically connected to the ground side, but the present invention is not limited to this. For example, the first conductor 21A and the second conductor 21B When the electric capacity of the two conductors 21B is sufficiently large, it is not necessary to electrically connect to the ground side.

  In the above-described embodiment, the width direction dimensions of the first conductor 21A and the second conductor 21B are larger than the width direction dimension of the separation pad 19C, but the present invention is not limited to this, and the first conductivity The width direction dimensions of the body 21A and the second conductor 21B may be equal to or smaller than the width direction dimension of the separation pad 19C.

In the above-described embodiment, the second conductor 21B is provided, but the present invention is not limited to this, and the second conductor 21B may be eliminated.
In the above-described embodiment, the first conductor 21A and the second conductor 21B are rotatable rollers. However, the present invention is not limited to this, and the first conductor 21A and the second conductor 21B are not limited thereto. At least one of them may be constituted by, for example, a cloth, a metal plate, or a metal brush that is in sliding contact with the sheet.

  In the above-described embodiment, the resistance portion described in the claims is configured by the separation pad 19C. However, the present invention is not limited to this, and for example, the rotation stops when the sheet is fed out. Thus, a retard roller or the like that imparts frictional resistance to the sheet may be used.

  The present invention is not limited to the above-described embodiment as long as it matches the gist of the invention described in the claims.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 3 ... Housing | casing 3A ... Discharge port 3B ... Discharge tray 3C ... Cover 5 ... Image forming part 7 ... Developing cartridge 7A ... Developing roller 7B ... Storage part 8 ... Photosensitive drum 8A ... Charger 9 ... Exposure device 11 DESCRIPTION OF SYMBOLS Fixing device 13 ... Transfer part 15 ... 1st feeder mechanism 15A ... Pickup roller 15B ... Separation roller 15C ... Separation pad 15D ... 1st guide part 17 ... Paper feed tray 19 ... 2nd feeder mechanism 19A ... Pickup roller 19B ... Separation roller 19C ... Separation pad 19D ... 2nd guide part 21A ... 1st conductor 21B ... 2nd conductor 23A ... Registration roller 23B ... Pinch roller

Claims (10)

An electrophotographic image forming apparatus for forming an image on a sheet,
A transfer portion for transferring the developer image to the sheet;
A separation roller that rotates in contact with the sheet and feeds the sheet to the transfer unit side;
A resistance portion that is disposed at a position facing the separation roller, and that imparts a conveyance resistance due to friction by contacting the sheet from the same side as the transfer portion;
A first conductor that is provided in a conveyance path of the sheet from the resistance unit to the transfer unit, and that is in contact with at least a part of the sheet that is in contact with the resistance unit, made of a conductive material. An image forming apparatus.   The image forming apparatus according to claim 1, wherein the first conductor is electrically connected to a ground side.   3. The image forming apparatus according to claim 2, wherein an electrical circuit that electrically connects the first conductor and the ground side is provided with an electrical resistance portion having electrical resistance. When the width direction is a direction orthogonal to the sheet conveyance direction and parallel to the sheet surface on which the image is formed,
4. The image forming apparatus according to claim 1, wherein a width direction dimension of the first conductor is larger than a width direction dimension of the resistance portion. 5.   5. The second conductor made of a conductive material that comes into contact with the sheet from a side opposite to the first conductor is provided at a position facing the first conductor. 6. The image forming apparatus according to claim 1. A paper feed tray provided on the lower side of the apparatus main body and on which a plurality of sheets can be placed;
A first guide unit that guides the sheet fed from the sheet feeding tray to the transfer unit side;
A second guide part that guides the sheet fed by the separation roller to the transfer part side,
The first conductor is provided on the transfer unit side from a portion where a conveyance path configured by the first guide unit and a conveyance path configured by the second guide unit merge. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the resistance portion is a separation pad having a plate-shaped portion that contacts the sheet. Comprising a photosensitive drum carrying a developer image;
The image forming apparatus according to claim 1, wherein the transfer unit directly transfers the developer image carried on the photosensitive drum onto a sheet.   The image forming apparatus according to claim 1, wherein the first conductor is a rotatable roller.   The image forming apparatus according to claim 5, wherein the second conductor is a rotatable roller.

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